Leonardo da Vinci’s ‘helicopter’ design could make drones quieter

A flying machine designed by Leonardo da Vinci may have been functional and much quieter than modern drone designs.

Rajat Mittal at Johns Hopkins University in Maryland and his colleagues have found that da Vinci’s “aerial screw”, which he proposed while working as a military engineer in 1480 but never built or tested, may require less power to generate the same amount of lift as a conventional drone rotor.

The machine is similar to an Archimedes’ screw, a helix-shaped pump that transports water as it rotates. Da Vinci envisaged the aerial screw as being powered by humans, which would have made it challenging to get off the ground due to weight. But with light electric motors spinning the rotor, it could have actually flown.

Mittal and his team built a simulation of the screw and put it in a virtual wind tunnel to see how it would perform while hovering in place, testing it at different rotational speeds and comparing it with a conventional drone rotor with two blades.

They found the aerial screw could generate the same amount of lift while rotating more slowly, meaning it would consume less power.

By measuring the pressure and wind flow patterns that moved around the virtual screw, Mittal and his team could also calculate how much sound it might produce, which they found was less than the conventional design for the same amount of lift.

“We were surprised,” says Mittal. “We went in thinking that because the shape of this spiral screw is just completely, in some sense, ad hoc, it was intuitive that the aerodynamic performance would be so bad that we would not be able to get any improvements over conventional blades.”

Mittal and his team now want to see if they can improve upon da Vinci’s design to make it more efficient while keeping its noise-reducing qualities, he says.

As drones are increasingly used in cities, such as for home deliveries or emergency services, noise pollution has become more of a problem, leading to researchers looking for new rotor designs that create less noise for a similar amount of lift.

“The authors do a good job of stating that if you can create the same thrust by turning slower, which the da Vinci [rotor] does, then the noise is going to be less,” says Sheryl Grace at Boston University in Massachusetts. “It doesn’t have to be the da Vinci design to achieve this, but it is nice that da Vinci’s does.”

However, to show that da Vinci’s design could be useful in real-world scenarios, they would need to test how it performs while flying through the air, rather than just hovering, as well as consider how the extra weight of the rotor might affect performance, says Grace.

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